SIM908 GPS Active antenna unable to acquire fix – Solution

The idea was to use SIM908 to send data to server through TCP at set intervals to server.

Problem faced:

We used long wire active antenna and designed according to the reference circuit but were not able to get the signal even when the device was kept in the open sky. The board image is shown below,


Solution :

We contacted Excelpoint systems for help and their Field Application Engineer Mr. Sivakumar B was able to figure out the mistake we did. 

In the hurry, we forgot that the reference circuit was for passive antenna and we didn’t take care of the bias voltage required for the operation of active antenna. This part is clearly mentioned in the SIM908 hardware design guide as shown below. 

So, all we needed to do was to provide a connection between pins GPS-VANT-OUT and GPS-VANT-IN. I did that with just a short circuit using soldering lead as both were adjacent pins as shown below, and SIM908 was able to acquire GPS signal and location fix in less than a minute. 

Hope it helps someone 🙂

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